1. Field of the Invention
This invention relates to methods for detecting specific extracellular nucleic acid in plasma or serum fractions of human or animal blood associated with neoplastic or proliferative disease. Specifically, the invention relates to detection of nucleic acid derived from human viruses associated with human neoplasia, and to methods of detecting and monitoring extracellular viral nucleic acids found in the plasma or serum fraction of blood by using nucleic acid amplification with or without enrichment for viral DNA. In particular, the invention relates to the detection, identification, or monitoring of the existence, progression or clinical status of human neoplastic disease caused by or associated with viral infection through detection of viral nucleic acid in plasma or serum fractions. The invention permits the detection of extracellular, viral nucleic acid in the serum or plasma of humans or other animals recognized as having a neoplastic or proliferative disease or in individuals without any prior history or diagnosis of neoplastic or proliferative disease. The invention specifically provides methods for early identification of cervical carcinoma, cervical carcinoma in situ, cervical dysplasia, cervical intraepithelial neoplasia (CIN) and penile squamous cell carcinoma associated with infection by oncogenic human papillomavirus subtypes.
2. Background of the Related Art
Cervical carcinoma is a common form of malignancy afflicting women, arising from the squamous epithelium of the cervix. Much is known of the natural history of this disease. The vast majority of cases are attributable, at least in part, to an infection by a papillomavirus of the cervical epithelium. In particular, certain subtypes of human papillomavirus (HPV), including HPV subtypes 16, 18, 31, 33, and 35, are associated with cervical malignancy, where HPV infection seems to alter the epithelium to predispose an individual to the development of cancer. This alteration of the epithelium by viral infection initially leads to cervical premalignant states, specifically cervical dysplasia or cervical intraepithelial neoplasia (CIN). Cervical dysplasia/CIN is important for recognizing, diagnosing, and treating women at risk for developing cervical cancer, because surgical removal of dysplastic epithelium reduces and may even eliminate the risk of development of cervical cancer.
A prominent advance over the past several decades has been the reduction of the incidence of cervical carcinoma in the United States. In general, this advance has been attributed to the routine gynecologic examination and the introduction of the Pap smear, based upon cervical cytology. A scraping of the cervical epithelium is taken and eventually smeared on a glass slide for staining and microscopic examination. These procedures, typically carried out in a medical clinic by skilled personnel and forwarded to a laboratory for examination by technologists or specially developed machines, are useful in identifying early premalignant states. Surgical removal or destruction of the affected portion of the cervix can then be undertaken by a gynecologist, resulting in a marked reduction in the risk of development of carcinoma (although potentially associated with difficulty in child-bearing or infertility). Unfortunately, the Pap smear does not detect all instances of cervical dysplasia or premalignancy. The current acceptable rate of false negatives (i.e., women who do have dysplasia according to an expert panel of pathologists looking at tissue biopsies rather than smear samples, but are not diagnosed that way during the routine smear screening) is roughly 5-10% but recent studies suggest that the actual rate may be much higher. Furthermore, in approximately 7-8% of cases, the Pap smear demonstrates atypical squamous cells of undetermined significance (ASCUS). In an additional 20-30% of cases, the Pap smear may be insufficient for interpretation due to the presence of inflammatory cells.
Human papilloma virus (HPV) is a papillomavirus that very frequently infects a number of human tissues, including cervical tissue, and infection of cervical tissues is associated with the development of cervical carcinoma. The changes in cervical tissues attributable to viral infection are not visible to the unaided eye, but viral infection is evident at the microscopic level by changes in the epithelial cell""s nucleus and cytoplasm that can be detected in a Pap smear. However, HPV infection cannot be detected in all cases of cervical dysplasia/pre-malignancy or even of cervical carcinoma. At least some of the failure to detect premalignancy using Pap smears as discusses above are the result of failure to detect HPV infection in cervical tissue samples.
HPV has many subtypes, and the subtypes may be distinguished by several methods. One commonly used method for evaluating exposure in humans to specific HPV subtypes, including those associated with cervical cancer, is by testing serum for antibodies against the viral subtype. Unfortunately, this method identifies both individuals with prior HPV exposure but without persistent infection and those with persistent infection, but does not distinguish between ongoing, persistent, and chronic HPV infections. This distinction is important, because persistent infection with HPV is associated with the greatest risk for development of cervical neoplasia. Because only a small percentage of women will develop cervical cancer within ten years of infectious exposure, active HPV infection is eliminated prior to the development of cervical premalignancy for most exposed women (Chua et al., 1996, Int. J. Cancer 68: 54-59). Serologic testing for HPV antibodies thus does not correlate well with the presence of cervical dysplasia, because it does not permit discrimination between previous HPV exposure and persistent HPV infection (Olsen et al., 1996, Int. J. Cancer 68: 415-419).
A second common method for screening women for specific HPV subtypes detects double stranded DNA viral genome (see, for example, Manos, U.S. Pat. No. 5,705,627; Bauer, U.S. Pat. No. 5,639,871; Bauer, U.S. Pat. No. 5,527,898; Manos, U.S. Pat. No. 5,283,171; Manos, U.S. Pat. No. 5,182,377; Gravitt et al., 1998, J. Clin. Microbiol. 36: 3020-3027). Those subtypes particularly associated with cervical cancer may be specifically amplified and detected using nucleic acid amplification methods, thereby identifying humans at high risk for the development of cervical carcinoma. Current methods for detecting HPV DNA entail evaluating cervical smear specimens directly for the viral DNA (see Silverstein, U.S. Pat. No. 5,814,448). This method is disadvantageous because the examiner may miss an infected region of the cervix, or the infected lesion may not be superficial and readily accessible, so that the test provides a false-negative result. Furthermore, as this method of testing for HPV DNA requires a gynecologic exam, DNA testing of cervical smears remains an imperfect method of screening the general female population because such exams are avoided by many women despite medical recommendations to the contrary.
In addition, HPV infection is a sexually transmitted disease, and males may carry the virus as asymptomatic carriers. Typically, cervical infection takes place at the time of sexual intercourse, and most of the risk factors (unprotected intercourse, multiple sexual partners, immunodeficiency, etc.) that apply to other sexually transmitted diseases also apply to HPV infection. Men may be infected by one or more HPV subtypes and can transmit one or more of these to their sexual partners. Although in most instances men serve only as carriers of the viral infection, in relatively rare cases they may develop squamous cell carcinoma of the penis in a manner analogous to cervical dysplasia and carcinoma in women. Both sexes may also develop anogenital warts, called condyloma accuminata, if infected by certain species of HPV, and these lesions may also be premalignant. Direct tissue swabs of the male urethra are not an effective general screening approach for detecting such carriers in the male population.
An attractive alternative approach to detecting HPV DNA in both women and men is testing peripheral blood for HPV DNA. However, it is not known in the art that papillomavirus DNA can be detected in the blood of individuals without cancer. Further, it is not known to the art whether papilloma virus can be detected in plasma and serum as an indication of persistent infection or risk for dysplasia or carcinoma.
Although many viruses have been shown to circulate in plasma and serum, the presence of systemically circulating extracellular HPV DNA has not been described in either the acute or chronic HPV infection. HPV infections tend to be localized as intracellular epithelial infections, and do not typically present with systemic clinical manifestations. Although metastatic circulating cervical cancer cells and leukocytes have been shown to have intracellularly incorporated HPV in cases of advanced cancer (Tseng et al., 1999, J. Clin. Oncol. 17: 1391-1396), detection of extracellular or free HPV DNA in blood is unknown in the art. To the contrary, the prior art suggests that some viruses are not readily detectable in the blood of infected individuals. An example is herpes simplex virus, which like HPV is a sexually-transmitted virus spread by mucosal contact. It was known in the art that, although herpes simplex virus could be found in blood serum of neonates with neonatal herpes simplex viremia, such could not be found in serum from older children having herpes simplex encephalitis, despite the presence of the virus in the cerebrospinal fluid of these older children (Kimura et al., 1991, J. Infect. Dis. 164: 289-293). In addition, HPV does not present with systemic viremia, and even for viruses in which viremia has been reported, the likelihood of detecting systemic viremia is greatest near the time of initial infection. This makes screening of women for the HPV virus doubly impractical, since any such screening would most likely be performed well beyond the period of initial exposure to the virus in the majority of cases.
One of the present inventors has shown that tumor-associated extracellular nucleic acids circulate in the plasma and serum of humans and animals (U.S. Ser. No. 08/818,058, the entire disclosure of which has been incorporated by reference). In particular, this application disclosed that tumor-associated DNA could be detected in the plasma and serum of humans and animals without cancer, enabling premalignancy to be detected, diagnosed, and monitored, and further, that individuals without cancer could be stratified or selected for further evaluation on the basis of the presence of mutant oncogene-derived DNA in blood plasma or serum.
Thus, there is a need in the art to determine whether HPV-specific nucleic acid can be detected in blood plasma or serum, and whether detection of HPV nucleic acid can be associated with the existence of cervical dysplasia or premalignancy. Improved screening methods having advantages over gynecological examinations and Pap smears would be enabled upon such a demonstration.
The present invention provides methods for detecting extracellular papillomavirus nucleic acid in blood or blood plasma or serum in a human or animal. The methods of the invention comprise the steps of extracting the nucleic acid from blood, plasma, or serum, specifically amplifying a portion of the extracted nucleic acid wherein the portion comprises a papillomavirus nucleic acid or a fragment thereof, and detecting the amplified product of the papillomavirus nucleic acid or fragment.
In a first aspect, the present invention provides methods for detecting papillomavirus DNA in blood or blood fractions, including plasma and serum, in a human or animal for detection, diagnosis, monitoring, treatment, or evaluation of neoplastic disease, including early cancer, non-invasive cancer, carcinoma in-situ, premalignancy, invasive cancer, and advanced cancer. In this aspect, the method comprise the steps of extracting DNA from blood or blood plasma or serum, amplifying a fraction of the DNA wherein said fraction comprises papillomavirus DNA, and detecting the amplified product of papillomavirus DNA.
The invention further provides methods for detecting extracellular papillomavirus DNA in bodily fluids other than those of the genital-urinary tract, including but not limited to whole blood, plasma, serum, effusions, ascitic fluid, saliva, cerebrospinal fluid, gastrointestinal secretions, and bronchial secretions including sputum, from a human for detection, diagnosis, monitoring, treatment, or evaluation of neoplastic disease, including early cancer, non-invasive cancer, carcinoma in-situ, premalignancy, invasive cancer, and advanced cancer. In these embodiments, the methods comprise the steps of extracting DNA from said bodily fluid, amplifying a fraction of the DNA wherein said fraction comprises papillomavirus DNA, and detecting the amplified product of papillomavirus DNA.
The invention further provides methods for detecting papillomavirus RNA in blood or blood fractions, including plasma and serum, in a human or animal for detection, diagnosis, monitoring, treatment, or evaluation of neoplastic disease, including early cancer, non-invasive cancer, carcinoma in-situ, premalignancy, invasive cancer, and advanced cancer. In these embodiments, the methods comprise the steps of extracting RNA from blood or blood plasma or serum, enzymatically converting the RNA into cDNA, amplifying a fraction of the cDNA wherein said fraction comprises papillomavirus cDNA, and detecting the amplified product thereof.
The invention further provides methods for detecting extracellular papillomavirus RNA in bodily fluids other than those of the genital-urinary tract, including but not limited to whole blood, plasma, serum, effusions, ascitic fluid, saliva, cerebrospinal fluid, gastrointestinal secretions, and bronchial secretions including sputum, from a human as an aid in the detection, diagnosis, monitoring, treatment, or evaluation of neoplastic disease, including early cancer, non-invasive cancer, carcinoma in-situ, premalignancy, invasive cancer, and advanced cancer. In these embodiments, the methods comprise the steps of extracting RNA from said bodily fluid, enzymatically converting the RNA into cDNA, amplifying a fraction of the cDNA wherein said fraction comprises papillomavirus cDNA, and detecting the amplified product of papillomavirus RNA.
The invention provides a diagnostic kit enabling detection of papilloma virus nucleic acid in blood or other bodily fluids, wherein the kit comprises primers specific for amplifying a fragment of human papillomavirus DNA, and optionally further comprises reagents, including salts, buffers, deoxynucleotide triphosphates or solutions thereof, and preparations of a polymerase, most preferably a thermostable polymerase, for amplifying said human papillomavirus nucleic acid fragments. In alternative embodiments, the kits further comprise salts, buffers, deoxynucleotide triphosphates or solutions thereof, and preparations of an enzyme, most preferably reverse transcriptase, for converting human papillomavirus RNA into cDNA.
The invention further provides methods for detecting extracellular papillomavirus nucleic acid, including HPV DNA and RNA, in blood, plasma, serum, and other bodily fluids, without amplification of the nucleic acid, for detection, diagnosis, monitoring, or evaluation of malignant or premalignant disease, including malignancies and premalignancies of the cervix. In these embodiments, the methods comprise the steps of extracting nucleic acid from blood or a blood fraction, specifically plasma or serum, to prepare extracted nucleic acid; specifically hybridizing a probe to a portion of the extracted nucleic acid, wherein the portion of the extracted nucleic acid is a papillomavirus nucleic acid; and detecting the hybridized papillomavirus nucleic acid. In preferred embodiments, nucleic acid extraction may be performed concurrently with hybridization of nucleic acid. In preferred embodiments, said hybridization is performed at a stringency sufficient for the probe to specifically hybridize to papillomavirus DNA and not non-specifically cross-hybridize to non-papillomavirus DNA.
In preferred embodiments of the inventive methods, papillomavirus DNA is extracted from blood plasma or serum using an extraction method selected from a group consisting of gelatin extraction method; silica, glass bead, or diatom extraction method; guanidinium thiocyanate acid-phenol based extraction methods; guanidinium thiocyanate acid based extraction methods; centrifugation through a cesium chloride or similar gradient; phenol-chloroform based extraction methods; or other commercially available nucleic acid extraction methods.
In preferred embodiments of the inventive methods, papillomavirus DNA is amplified using an amplification method selected from a group consisting of polymerase chain reaction; ligase chain reaction; DNA signal amplification; Q-beta replication; transcription-based amplification; isothermal nucleic acid sequence based amplification; self-sustained sequence replication assays; boomerang DNA amplification; strand displacement activation; cycling probe technology; and any combination or variation thereof.
In preferred embodiments of the inventive methods, detection of the amplified papilloma virus DNA product is performed using a detection method selected from a group consisting of gel electrophoresis; ELISA detection including modifications, including biotinylated or otherwise modified primers; hybridization using a specific, fluorescent-, radioisotope-, or chromogenically-labeled probe; Southern blot analysis; electrochemiluminescence; reverse dot blot detection; and high-performance liquid chromatography.
In another preferred embodiment, the invention provides a method for evaluating a human for cervical malignancy or premalignancy, wherein the method comprises two or more tests performed either in a concurrent or sequential fashion, wherein one test evaluates plasma or serum for the presence of HPV DNA, and a second test is either a pap smear, a bimanual pelvic examination, a tissue biopsy, or a colposcopy.
The methods of the invention can identify humans or animals having persistent papillomavirus infection, thereby identifying humans at risk for developing or who have in fact developed a neoplastic, premalignant, or malignant disease associated with papillomavirus. In certain embodiments, these methods comprise the steps of extracting nucleic acid, said nucleic acid being DNA or RNA, from a bodily fluid, including but not limited to blood plasma or serum, amplifying a fraction of the extracted nucleic acid wherein said fraction comprises papillomavirus nucleic acid, detecting the amplified papillomavirus nucleic acid product; and performing said steps in a repetitive or serial manner, wherein detection of the amplified papillomavirus nucleic acid product serially or repetitively identifies a human or animal having a persistent papillomavirus infection, said human or animal thereby being at high risk for developing or having a disease associated with papillomavirus.
The methods of the invention are useful if providing a prognosis of malignant disease in a human, and for determining a predisposition to cancer in a human.
The methods of the invention comprise diagnostic methods for identifying humans at risk for developing or who have malignancy or premalignancy of the epithelium, these malignancies including but not limited to cervical, penile and squamous cancers, and these premalignancies and carcinoma in-situ including but not limited to cervical dysplasia and cervical intraepithelial neoplasia (CIN).
The methods of the invention further comprise methods to identify or select a human having an HPV-containing malignancy or premalignancy. The invention thereby provides methods to identify, stratify, or select a human who might benefit from an HPV-directed therapy, or from a further diagnostic test or therapeutic procedure, including but not limited to a bimanual pelvic exam, Pap smear, colposcopy, biopsy, endocervical currettage, conization of the cervix, and anti-viral therapies.
It is therefore the object of this invention to detect or infer the presence of papilloma virus-positive cancerous or precancerous cells within a human having a recognized cancer or pre-cancer, and in those not previously diagnosed, by examining the plasma or serum fraction of blood, or examining other bodily fluid, for papilloma virus nucleic acids in either a qualitative or quantitative fashion.
One advantageous application of this invention is for identifying individuals having epithelial malignancies and premalignancies. Another advantageous application of this invention is for selecting individuals for HPV-or disease-directed therapies, including biotherapies, chemotherapies, anti-viral therapies, radiation therapies, and surgical therapies. Yet another advantageous application of the methods of this invention is to provide a marker for determining whether an adequate therapeutic effect has been achieved by a therapy, or whether additional or more advanced therapy is required, and to assess prognosis in these patients. A further advantageous application of this invention is to permit identification or analysis, either quantitatively or qualitatively, of papillomavirus nucleic acid in plasma or serum of humans during or following surgical procedures to remove premalignant or malignant lesions, and thus allow stratification of such patients as to their risk of residual cancer following the surgery, and their need for further therapy. It is also an advantageous application of this invention to allow identification or analysis of papilloma virus nucleic acid, either qualitatively or quantitatively, in the blood or other bodily fluid of a human who has completed therapy as an early indicator or relapsed cancer, impending relapse, or treatment failure. Another advantageous application of this invention is to allow identification of persistent papilloma virus infection through serial analysis of blood or body fluid samples as a method of stratifying risk of development of pre-malignant or malignant disease or prognosis.
Specific preferred embodiments of the present invention will become evident from the following more detailed description of certain preferred embodiments and the claims.